1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method, a semiconductor device manufacturing apparatus, a semiconductor device manufacturing system, and a cleaning method for a semiconductor device manufacturing apparatus. More specifically, it relates to a semiconductor device manufacturing method, used in a film formation process such as a CVD method, a semiconductor device manufacturing apparatus, a semiconductor device manufacturing system, and a cleaning method for a semiconductor device manufacturing apparatus.
2. Description of the Related Art
Usually, in a film formation process in a manufacturing process of a semiconductor device, a desired thin film is formed on a wafer to be processed by a film formation apparatus. Then, to check whether the thus formed thin film has a desired film thickness, the wafer is taken out of the reaction chamber (processing chamber) of the film formation apparatus to measure the film thickness using a film-thickness measurement device separate from the film formation apparatus.
Recently, there has been suggested a semiconductor device manufacturing apparatus which measures the thickness of a film in-situ concurrently with a film forming step in order to control the film thickness at higher accuracy or to improve a production efficiency of the semiconductor device. For example, in a semiconductor device manufacturing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-82214, laser light is applied to a wafer on which a film is being formed in a quartz chamber (processing chamber) from the outside thereof. Then, the intensity of the light reflected by optical interference in the thus formed thin film on the wafer is measured outside the quartz chamber. Thus, the film thickness of the thin film deposited on the wafer is measured concurrently while it is being formed.
Furthermore, in a vacuum CVD apparatus disclosed in Jpn. Pat Appln. KOKAI Publication No. 4-343220, a quartz plate is disposed together with a port having a wafer (semiconductor substrate) mounted thereon in a furnace tube (processing chamber). Then, upon the start of film formation, light from a halogen lamp is applied to the quartz plate. Then, an intensity change of light transmitted through the quartz plate is detected to thereby measure the thickness of a film deposited on the quartz plate during the film formation. Then, the thickness of the film deposited on the quartz plate is sequentially checked during the film formation against beforehand obtained conditions of the film formation, thereby indirectly measuring the thickness of the thin film deposited on the wafer concurrently while the film is being formed.
Furthermore, to form a better thin film, there is contrived a semiconductor device manufacturing apparatus equipped with a cleaning mechanism for cleaning the interior of the processing chamber in which a wafer is housed. For example, in a semiconductor device manufacturing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-206822, an etchant gas is introduced into a reaction tube (processing chamber) made of quartz or the like. Thereby, a film deposited on the inner wall of the reaction tube is etched off for cleaning. In this case, laser light is applied from a laser light emitter disposed outside the reaction tube so as to pass inside. Then, a detector disposed opposite the laser light emitter, the other side of the reaction tube, is used to monitor (observe) the intensity change of the laser light transmitted through the reaction tube. Since the film deposited on the reaction tube is thin near the end of the etching processing, the intensity of the transmitted laser light increases. When the deposited film disappears from the reaction tube, the intensity of the transmitted laser light becomes a roughly constant level. Thereby, it is confirmed that the interior of the reaction tube has been cleaned, thus detecting the end of etching.
As described above, the technologies disclosed in Jpn. Pat Appln. KOKAI Publication Nos. 4-82214, 4-343220 and 4-206822 have roughly two problems of apparatus configuration (processing environment and conducting environment) and measurement accuracy which will be described below.
As in the respective inventions described above, in a configuration in which a measuring light such as laser light passes through the interior of the processing chamber, it is necessary to maintain an optical path in the processing chamber. Meanwhile, noise which deteriorates the measurement accuracy is caused by fluctuating wafer temperature, gas introduced into the processing chamber, and the atmosphere inside the processing chamber. Therefore, to prevent the noise from occurring in the information of the measuring light, it is necessary to arrange the optical path at an optically sufficiently stable position. This may cause various restrictions on the construction of the processing chamber. Furthermore, it is necessary that at least a region (space) which corresponds to the optical path in the processing chamber should be optically sufficiently stable. This may place restrictions atmospheric conditions in the processing chamber, components of materials (gas or the like) used in film formation processing, components of a gas (etchant gas) for cleaning, etc. This may in turn place restrictions on service conditions of the semiconductor device manufacturing apparatus (vacuum CVD apparatus).
In addition, according to the technology disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-343220, the thickness of a film deposited on a quartz plate arranged in a processing chamber is measured to indirectly measure the film thickness of a thin film deposited on a wafer. If this indirect measurement is used, a measurement subject piece such as the quartz plate is typically positioned as close as possible to the wafer to improve the measurement accuracy. As mentioned above, however, the optical path for measurement needs to be optically sufficiently stable. Therefore, it is necessary to arrange a measurement system including the measurement subject piece and the optical path at a position where the measuring light is scarcely affected by a temperature change of the wafer and the like. Therefore, it is difficult to simply bring the measurement subject piece close to the wafer in order to improve the measurement accuracy.
On the other hand, if the measurement subject piece is brought too close to the wafer, it might disturb a proper flow of film formation gas in the vicinity of the wafer. Alternatively, the temperature change of the measurement subject piece itself might disturb a properly preset atmosphere in the vicinity of the wafer. As understood from the above, if the measurement subject piece is carelessly arranged too close to the wafer with the intention of improving the measurement accuracy, it may rather deteriorate the film quality and the like of the thin film formed on the wafer.
As discussed above, when the film thickness of the thin film deposited on the wafer is indirectly measured, it is difficult to set the measurement system, and the apparatus configuration is usually complicated. Particularly, in a batch processing apparatus, for sweepingly processing a plurality of wafers in a batch as by the technology disclosed in Jpn. Pat. Appln. KOKAI Publication 4-343220, it is liable to become more difficult to reconcile the improvement in measurement accuracy with a higher degree of freedom of the apparatus configuration. In a batch processing apparatus, a plurality of wafers are arranged at different positions. In this state, taking into account the above-mentioned intra-apparatus constructional restrictions, it is extremely difficult to further improve the measurement accuracy for the plurality of wafers while maintaining a roughly uniform measurement accuracy level for the respective wafers.
Furthermore, as by the technology disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-82214, taking into account the construction of the batch processing apparatus, it is also very difficult to directly measure the film thickness of a thin film on each of wafers by directly applying the measuring light onto all of the wafers during the film formation.